The present invention relates to a method of forming an isolation layer in a semiconductor device, and more particularly relates to a method of forming an isolation layer in a semiconductor device for improving a shift of a threshold voltage of an adjacent memory cell caused by an interference phenomenon of a cell.
As semiconductor devices become more high-integrated, the width of trenches becomes narrower and the depth of trenches becomes deeper, and so it is more difficult to completely gap-fill the trench with a high density plasma (HDP) oxide layer, which has been conventionally used, to form an isolation layer without creating a void. To solve the above-identified problems, a SOG (spin on glass) method is utilized. As compared with the method utilizing the high density plasma (HDP) oxide layer, however, the SOG method has the problem of shifting cycling threshold voltage of the semiconductor device.
To improve the problem of shifting cycling threshold voltage of the semiconductor device, an attack against the conductive layer should be prevented by securing a thickness of oxide layer formed on a side wall of the trench.
To secure a thickness of the oxide layer formed on a side wall of the trench, however, the thickness of the high density plasma (HDP) oxide layer should be increased when the high density plasma oxide layer is formed on a surface of the trench. But, the high density plasma (HDP) oxide layer forms an overhang on an upper area of the trench.
Due to the above-described overhang, it is difficult to form a high density plasma (HDP) oxide layer having a thickness of 1,000 Å or more.